There is a tendency in discussing evolutionary psychology toward confusion over what should be the proper null hypothesis. To put it simply, what do we assume* in the absence of evidence for an hypothesis?
This confusion is not specific to evolutionary psychology. It is a problem whenever we talk about studying topics in which many of us already consider ourselves experts. Being human, we are, of course, all experts on what that means. Or we think we are. So we think we know what base assumptions about humanity we should use absent any evidence to the contrary.
The fact of the matter is, however, that we are not experts, not most of us. We haven’t studied the huge bodies of literature coming out of anthropology, psychology, and sociology that would be required to have to the first clue what kind of assumptions are warranted. Our assumptions are based on “Everybody knows” and some very simplified understanding of biology and living in a world in which variability is to a large degree defined as dysfunction. They are rarely nuanced or complex.
This means that when we hear someone arguing against a particular interpretation of data, when we hear someone say that a hypothesis was not supported, we tend to think that person is arguing for a null hypothesis that is…well, somewhat out there. Someone tells us that the data is insufficient to determine whether a particular difference observed between two groups is genetic, and far too many of us hear that person assert that there is no genetic influence on behavior. Genetic influence is treated as an all-or-nothing proposition.
I know. When I put it like that, it sounds a bit silly, but it happens with amazing regularity.
Greg Laden put a post up today that should help people think about what the null hypothesis is when it comes to evolutionary psychology and what differences need to be teased apart between that and experimental hypotheses in order for evolutionary psychology to make claims about the selection of particular behaviors:
In both cases, one could say that there is a “mental module” … a neural structure in the brain that is good at doing some thing. In both cases one could say that the module emerged as part of the evolutionary process. Indeed, I regard the result of this and similar experience as very strong evidence that there are modules in human brains that are really good at doing certain things, and that are sufficiently specialized that they are also bad at doing similar but in some sense “unnatural” versions of the same thing. In an Evolutionary Psychology version, the module was mostly built neurologically because of genetically specified development. In a more general Darwinian Psychology, brains are selected (though evolutionary process) to be good at learning how to do this sort of thing.
That–that difference between a brain that has evolved to produce particular specific, detailed behaviors and a brain that has evolved to be rather flexible in how it learns to accomplish much broader tasks–that is the battle that is happening. The question isn’t absolute freedom versus determinism. The questions are ”To what specificity are our behavioral capacities and tendencies determined?” How complex a system of modules do we need to posit to describe these human behavioral capacities and tendencies? (This is, of course, before we get to the question of whether those modules are adaptive, a discussion I can’t deal in the generalities of.)
Given that human beings have an exceptionally long childhood (i.e., period of dependence on others) that we spend sucking up cultural practices like little sponges, this is a very hard question to answer. Good research, research that can address that difference, is hard to come by–harder in an age of increasingly global culture. Think about the spread of musical styles in the last couple of decades if you want some idea of the cultural “contamination” a researcher has to deal with.
There are ways to get at the differences. Greg gives an example of a study that is fairly clever and nicely suggestive of a broader trait, one observed in other species with much less apparent cultural influences, being translated through culture. Or translating culture. It’s kind of cool.
Other research in evolutionary psychology is, simply put, much less sophisticated. It uses single-culture samples. It uses measurement tools that, rather than trying to distinguish between individual behaviors and underlying motivation or traits, as would be necessary to differentiate these sorts of hypotheses from the null hypothesis, treat the behaviors as a proxy for what is being tested.
Not all evolutionary psychology research does this sort of thing, of course, but much of it does, and much of that research produces “sexy” results. Literally, these results often have to do with sex and the controversies that surround it. This research gets media attention for providing simple answers to questions we find interesting and important.
The methodological shortcomings mean that there will be critiques of these studies. The controversial nature of the topics studied mean those critiques will get attention. The fact that this kind of research keeps being done means that those critiques will be repeated and often won’t be presented in full each time.
This makes straw-manning the critiques fairly easy, either intentionally by those with an interest in creating a positive perception of the research or unintentionally because of our individual perceptions of expertise where we have none. It is easy to say, “How can you reject that? Do you think genes have no effect on our brains and behavior?”
The answer is, as I hope is clear by now, “Don’t be silly.”
Okay, a more full answer is that of course we recognize that genes have a direct effect on the brain. Without genes, we wouldn’t have brains. However, that isn’t what it means when we reject the idea, based on lack of discriminatory data, that a particular behavior is driven by our genes.
It means that, given just how flexible our brains are, the body of research produced so far has failed to prove that this particular behavior, at this particular level of granularity, is determined by our genes. The null hypothesis, that our genes are responsible more generally for the organization of our brains and behavior, still stands.
*I’m using the word “assume” in a slightly unorthodox manner here. I mean to hold preliminary conclusions that could be contradicted by further data, not make baseless or unexamined guesses. However, if you think about it, that’s really what we generally mean by the word.